1. Field of the Invention
This invention relates to a process for preparing fast-setting magnesium phosphate cementitious compositions. More particularly, it relates to fast-setting cementitious compositions from superphosphoric acid.
2. Related Information
Fast-setting cementitious compositions having utility for various purposes for which concretes are employed have been heretofore known.
U.S. Pat. No. 3,202,520 (Enoch, Aug. 8, 1965) discloses a rapid set non-hygroscopic cement composition consisting essentially of a blend of a phosphate derived from phosphoric acid and of alumina, and containing from 15 to 55 weight percent of P.sub.2 O.sub.5 and from 45 to 75 weight percent of alumina, and from 5 to 18 weight percent of magnesium oxide. The phosphoric acid is used in its liquid state then moisture is removed by drying the blend above 122.degree. F.
U.S. Pat. No. 3,525,632 (Enoch, Aug. 25, 1970) discloses a rapid-setting concrete cement composition which comprises dry blending magnesium-containing compounds, aluminum-containing compounds and phosphorus-containing compounds from stated sources in stated weight percentages, and then pulverizing the blended material without a separate drying stage. The phosphorus-containing compound is a mixture derived from phosphoric acid, and at least 50 weight percent of one of trimagnesium phosphate, aluminum orthophosphate, and phosphoric anhydride.
U.S. Pat. No. 3,879,209 (Limes et al., Apr. 22, 1975) discloses a process for making a fast-setting concrete comprising establishing a mixture of an aggregate containing at least 10 percent by weight of magnesia and ammonium phosphates in aqueous solution. This patent further discloses that a commercial (agriculture fertilizer) product known as sequestered phosphatic solution (SPS) is particularly suitable as the source of the ammonium phosphate. The ammonium component is an essential feature of this invention.
U.S. Pat. No. 4,059,455 (Limes et al., Nov. 22, 1977) discloses a process for making a fast-setting concrete comprising establishing a mixture of an aggregate, containing at least 1% magnesia, and ammonium phosphates in aqueous solution. Again, the ammonium component is essential for attainment of the desired results of the invention.
U.S. Pat. No. 4,174,227 (Tomic, Nov. 13, 1979) discloses a grouting system comprising an acidic reactive component comprising at least one acidic oxy phosphorus compound selected from phosphoric acids, anhydrides of phosphoric acids and salts of phosphoric acids with multivalent metal cations, and a basic reactive component comprising at least one basic metal compound of a Group II or Group III metal capable of reacting with the oxy phosphorus compound(s) in the presence of water to form a monolithic solid.
U.S. Pat. No. 3,821,006 (Schwartz, June 28, 1974) discloses a patching composition consisting essentially of a reactive component of MgO with an acid phosphate salt and an inert aggregate component. The particle size of the inert aggregate component is related to the compressive strength of the cement formed at an early cure age.
The mixtures employed in the methods of the patents discussed above set and develop usable strength much more rapidly than conventional materials. Nonetheless, each of these patents is limited (as discussed above) and therefore distinguishable from the processes of the present invention in several ways.
U.S. Pat. No. 3,475,188 (Woodhouse et al., Oct. 28, 1969) discloses a dry refractory composition consisting essentially of a liquid bonding agent absorbed onto an absorbent, up to 80% by weight being absorbed thereon, magnesium oxide and refractory aggregate. The liquid bonding agents disclosed include sulfuric acid, hydrochloric acid, chromic acid and phosphoric acid. The absorbents disclosed include Kieselguhr, bentonite, fuller's earth, chrome ore or mixtures thereof.